Apparatus for driving liquid jet head

Abstract

An apparatus for driving a liquid jet head comprises: a piezoelectric element which mechanically deforms responsive to an electric signal; a pressure chamber whose volume varies due to the deformation of such element; a discharge port communicated with such chamber; 1st and 2nd charging circuits to charge such element at the same polarity; a discharging circuit to discharge such element; and a control unit for making the 1st charging circuit operative prior to the operation of the 2nd charging circuit. A charge time constant of the 1st charging circuit is set to be sufficiently long that no droplet is emitted. A charge time constant of the 2nd charging circuit is set to be shorter to emit a droplet from the discharge port. The surface tension of the meniscus and the contractive force due to the contraction of the pressure chamber act multiplicatively, so that it is possible to record a droplet of a small dot diameter.

What we claim is: 
     
       1. A method of ejecting a droplet of a liquid from a discharge port in communication with a liquid chamber, comprising the steps of: reducing the volume of said liquid chamber without ejecting a droplet of liquid from said discharge port;   suddenly increasing the volume of said liquid chamber to retract a meniscus of the liquid from said discharge port;   suddenly reducing the volume of said liquid chamber, substantially immediately after said sudden increase in volume and in substantial synchronism with the maximum velocity of the natural recovery of the meniscus toward said discharge port, to eject liquid from said discharge port; and   increasing the volume of said liquid chamber to an original condition.   
     
     
       2. The method according to claim 1, further comprising controlling the volume to which said liquid chamber is reduced in said sudden volume reducing step.